are you the primary account holder?

Have you tried, https//my.t-mobile.com

I am the primary holder and I've used the tmobile url address. 

Have you tried a different web browser?  Edge is always a solid choice along with Brave, and Firefox for me.  Do you have any ad and cookie blockers potentially interfering with the site loading correctly?

I did try Edge and it did work. Thanks for your help syaoran.

I tried edge 

Same ting is happening to me, tried different browsers, different networks (wifi, cellular) different OSs, app on my phone doesn’t work either. Turns out that T-Mobile made the STUPID decision to block access from certain countries, taking the “easy” way out for security instead of investing in security tools and services to protect their web site(s) etc. No wonder that they had breaches in the past, poor security. VERY, VERY upset w/ T-Mobile at this time. Support is totally USELESS (outsourced), they were trying their easy way out, “it is blocked by the country you are in”…. Really ? Since when the EU is blocking its people from accessing T-Mobile ???? Besides that, I am an IT/Security Professional so all this is clearly BS. Upon return I’ll ask for money back for the service that is INCOMPLETE, w/o support and access to the app/website for cost control. Very, very upset. The “uncarrier” gets close to be booted for another cellular provider. BTW, ATT Wireless and Verizon Wireless DON’T block access from the country I am in. I gathered the needed information (screenshots, etc.) as evidence if needed (in court etc.).